Mounting tires on rims with automatic tire/rim mounters using a mechanical force is a practice that is used increasingly today. FIG. 3 shows an exemplary case of using such an automatic mounter to mount a pneumatic tire on a wheel, particularly one that has two dish-type rims connected in a bottom-to-bottom relationship, each rim having an annular hump in a position interior to the bead seat, with the bead of the tire engaging the bead seat between the hump and the rim flange and with an annular well of a smaller diameter than the bead seat being formed between the humps of the two rims. As shown, the wheel indicated by A is placed in such a way that the rotating face will lie horizontally. Then, the tire indicated by B is placed over the wheel A from above and the bead B.sub.1 which is located in the lower position (i.e., the bead on the back side of the tire) is first caused to traverse the rim flange A.sub.1 and the hump A.sub.3 which are located in the upper part of the wheel A, whereby it is seated within the well A.sub.5 between the humps A.sub.3 and A.sub.4 in the upper and lower positions, respectively. Subsequently, the bead B.sub.2 which is located in the upper position (i.e., the bead on the front side of the tire) is pressed down by means of expanding rollers C so that the bead is caused to traverse the upper rim flange A.sub.1 and hump A.sub.3 to become seated within the well A.sub.5. Thereafter, the tire is inflated, whereby the beads B.sub.1 and B.sub.2 on the front and back sides, respectively, of the tire will traverse the humps A.sub.3 and A.sub.4 in the upper and lower positions, respectively, so that they will be mounted in engagement both with the bead seat A.sub.6 between the rim flange A.sub.1 and the hump A.sub.3 and with the bead seat A.sub.7 between the rim flange A.sub.2 and the hump A.sub.4.
The conventional pneumatic tire, however, has had the problem that when one attempts to mount it on the wheel A having the two dish-type rims connected in a bottom-to-bottom relationship, part of the bead B.sub.1 on the back side which has been first caused to be located within the well A.sub.5 is not situated in the right position but it is partly caused to stop as it has run onto the hump A.sub.4 in the lower position. If it is the bead B.sub.2 on the front side that has run onto the upper hump A.sub.3, one may tread upon it by foot or otherwise press it down to become seated within the well A.
If part of the bead B.sub.1 on the back side of the tire runs onto the hump A.sub.4, the rotating axis of the tire B will not coincide with that of the wheel A and the tire B becomes eccentric with the rim (wheel A) as shown in FIG. 4, whereby insufficient engagement will occur between the two components when the tire B is inflated.
If one attempts to solve this problem by increasing the inside diameter of the bead B.sub.1 on the back side of the tire so that it will readily ride across the hump A.sub.4, the force of engagement that develops after inflating the tire decreases to such a level that the bead is offset from the bead seat on the rim, thereby causing a rim offset.